c This is the control file for the GEANT simulation. Parameters defined c in this file control the kind and extent of simulation that is performed. c The full list of options is given in section BASE-40 of the GEANT manual. c c In addition, some new cards have been defined to set up the input source c for the simulation. Three kinds of simulation runs are available, selected c by which of the following three "cards" are present below. c 1. Input from Monte Carlo generator (card INFILE) c 2. Built-in coherent bremsstrahlung source (card BEAM) c 3. Built-in single-track event generator (card KINE) c The order of the list is significant, that is if INFILE is present then the c BEAM and KINE cards are ignored, otherwise if BEAM is present then KINE is c ignored. For example, the 3-card sequence: c INFILE 'phi-1680.hddm' c SKIP 25 c TRIG 100 c instructs HDGeant to open ./phi-1680.hddm, skip the first 25 events and then c process the following 100 input events and stop. If the end of the file is c reached before the event count specified in card TRIG is exhausted then the c processing will stop at the end of file. TRIG 10000000 cINFILE 'rhop.hddm' cBEAM 12. 9. RUNG 9999 c Commenting out the following line will disable simulated hits output. OUTFILE 'hdgeant.hddm' c The following card enables single-track generation (for testing). c For a single-particle gun, set the momentum (GeV/c), direction c theta,phi (degrees) and vertex position (cm), and for the particle c type insert the Geant particle type code plus 100 (eg. 101=gamma, c 103=electron, 107=pi0, 108=pi+, 109=pi-, 114=proton). If you use c the particle code but do not add 100 then theta,phi are ignored c and the particle direction is generated randomly over 4pi sr. c For a listing of the Geant particle types, see the following URL. c http://wwwasdoc.web.cern.ch/wwwasdoc/geant_html3/node72.html c The meaning of the arguments to KINE are as follows. c - particle = GEANT particle type of primary track + 100 c - momentum = initial track momentum, central value (GeV/c) c - theta = initial track polar angle, central value (degrees) c - phi = initial track azimuthal angle, central value (degrees) c - delta_momentum = spread in initial track momentum, full width (GeV/c) c - delta_theta = spread in initial track polar angle, full width (degrees) c - delta_phi = spread in initial track azimuthal angle, full width (degrees) c c particle momentum theta phi delta_momentum delta_theta delta_phi KINE 103 4.0 0. 0. 0. 0. 360. c The SCAP card determines the vertex position for the particle gun. It c supports the following three arguments, all of which default to 0. c c vertex_x vertex_y vertex_z SCAP 0. 0. 0. c The FEMO card lets you specify the parameters of an iron Moller target c and insert it into the electron beam in the region between the goniometer c and the entrance to the tagger dipole. Parameters are as follows. Be sure c to add the decimal point to each number, otherwise it will not read in. c - motar_angle_deg = rotation angle about the x axis from perpendicular c - motar_thick_cm = thickness of the Moller iron target c - motar_z_cm = placement distance downstream of the goniometer c c motar_angle_deg motar_thick_cm motar_z_cm cFEMO 30. 1e-3 280. c If you specify a non-zero value for vertex_x and/or vertex_y above then c all tracks will emerge from the given point. If you leave them at zero, c you have the option of specifying the HALO card which causes the simulation c to generate events with a transverse profile modeled after the 12 GeV c electron beam. The argument only argument to HALO is fhalo, the fraction c of the beam that lies in the halo region surrounding the core gaussian. c The nominal value taken from CASA technical note JLAB-TN-06-048 is 5e-5. c This card is only effective for electron beam simulations with gxtwist. c c fhalo HALO 5e-5 c The following lines control the rate (GHz) of background beam photons c that are overlayed on each event in the simulation, in addition to the c particles produced by the standard generation mechanism. BGGATE expects c two values in ns, which define the window around the trigger time that c background beam photons are overlaid on the simulation. The value you c should enter for BGRATE depends on many details of the photon beam: the c endpoint energy, the low-energy cutoff to be used in generating beam c photons, the location of coherent edge, the electron beam spot size and c emittance at the primary collimator, the electron beam current, etc. To c find the setting that is right for you, follow these steps in order. c 1) Check the BEAM card above that it has correct values for the electron c beam energy (field 1) and the low-energy cutoff that you want to use c in your simulation (field 3). Remember these values. c 2) Open a new tab in a web browser and enter the following URL, c http://zeus.phys.uconn.edu/halld/cobrems/ratetool.cgi which displays c a form containing many fields describing the electron beam and the c photon beamline. Enter the correct values in all fields in the c left-most column of parameters. The right column of parameters c defines the windows over which the tool will compute integrals of c the beam rate. Set the "end-point" window to span the full range c from your beamEmin (see step 1 above) to the electron beam endpoint, c Then click the Plot Spectrum button. After a few seconds, the form will c respond with a few plots and rate numbers in bold text. Record the c value given for the "end-point rate". This is your BGRATE value. c 3) Enter your BGRATE value found in step 2 after BGRATE in the line c below, and remove any characters before the BGRATE keyword. You are c now ready to go. If you ever change anything in the beamline geometry c eg. the collimator diameter, the coherent edge position, or the value c of beamEmin, do not forget to come back and change your BGRATE. cBGGATE -200. 200. cBGRATE 4.80 c The above cards BGRATE, BGGATE normally cause the simulation to add c accidental tagger hits to the simulated output record, in addition to c adding these beam photons to the list of particles to be tracked through c the detector. If you want the accidental tagger hits to be added to the c simulated output record but you do not want to track the background c beam photons, remove the comment in front of BGTAGONLY below. c NOTICE: If you turn on BGTAGONLY then you might as well raise the c minimum energy of beam photons being generated to the lower bound of c the tagger energy range you are interested in, which might be 3 GeV for c low-intensity running, 7 GeV for high-intensity running, or even 8 GeV c if you are only interested in the region of the coherent peak. This c minimum is the third field of the BEAM card above. Remember that if c you change beamEmin, you also need to change BGRATE to match, as c described above. cBGTAGONLY 1 c The following card seeds the random number generator so it must be unique c for each run. There are two ways to specify the random see for a run. c 1. One argument, must be an integer in the range [1,215] c 2. Two arguments, must be a pair of positive Integer*4 numbers c In the first case, one of a limited set of prepared starting seeds is c chosen from a list. These seeds have been certified to produce random c sequences that do not repeat within the first 10^9 or so random numbers. c For cases where more choices are needed, the two-argument form gives c access to a total of 2^62 choices, with no guarantees about closed loops. RNDM 121 c The following line controls the cutoffs for tracking of particles. c CUTS cutgam cutele cutneu cuthad cutmuo bcute bcutm dcute dcutm ppcutm tofmax c - cutgam = Cut for gammas (0.001 GeV) c - cutele = Cut for electrons (0.001 GeV) c - cutneu = Cut for neutral hadrons (0.01 GeV) c - cuthad = Cut for charged hadrons (0.01 GeV) c - cutmuo = Cut for muons (0.01 GeV) c - bcute = Cut for electron brems. (CUTGAM) c - bcutm = Cut for muon brems. (CUTGAM) c - dcute = Cut for electron delta-rays. (10 TeV) c - dcutm = Cut for muon delta-rays. (10 TeV) c - ppcutm = Cut for e+e- pairs by muons. (0.01 GeV) c - tofmax = Time of flight cut (1.E+10 sec) c - gcuts = 5 user words (0.) CUTS 1e-4 1e-4 1e-3 1e-3 1e-4 1e-4 1e-4 1e-3 1e-3 1e-3 1e10 LOSS 1 c The following line controls a set of generic flags that are used to c control aspects of the simulation generally related to debugging. c For normal debugging runs these should be left at zero (or omitted). c At present the following functionality is defined (assumes debug on). c SWIT(2) = 0 turns off trajectory tracing c = 2 turns on step-by-step trace during tracking (verbose!) c = 3 turns on trajectory plotting after tracking is done c = 4 turns on step-by-step plotting during tracking c SWIT(3) = 1 stores track trajectories for plotting after tracking is done c SWIT(4) = 0 trace trajectories of all particle types c = 3 trace only charged particle trajectories SWIT 0 0 0 0 0 0 0 0 0 0 c The following card enables the GelHad package (from BaBar) c on/off ecut scale mode thresh GELH 1 0.2 1.0 4 0.160 c The following card selects the hadronic physics package c HADR 0 no hadronic interactions c HADR 1 GHEISHA only (default) c HADR 2 GHEISHA only, with no generation of secondaries c HADR 3 FLUKA (with GHEISHA for neutrons below 20MeV) c HADR 4 FLUKA (with MICAP for neutrons below 20MeV) HADR 4 c The following cards are needed if optical photons are being c being generated and tracked in the simulation. The CKOV directive c enables Cerenkov generation in materials for which the refractive c index table has been specified. The LABS card enables absorption c of optical photons. The ABAN directive controls a special feature c of Geant which allows it to "abandon" tracking of charged particles c once their remaining range drops below the distance to the next c discrete interaction or geometric boundary. Particles abandoned c during tracking are stopped immediately and dump all remaining energy c where they lie. The remaining energy is dumped in the correct volume c so this is OK in most cases, but it can cut into the yield of c Cerenkov photons (eg. in a lead glass calorimeter) at the end of c a particle track. If this might be important, set ABAN to 0. CKOV 1 LABS 1 c The following card prevents GEANT tracking code from abandoning the c tracking of particles near the end of their range, once it determines c that their fate is just to stop (i.e. electrons and protons). This c behaviour is normal in most cases, but in the case of Cerenkov light c generation it leads to an underestimate for the yields. c ABAN 1 abandon stopping tracks (default) c ABAN 0 do not abandon stopping tracks ABAN 0 c The following card sets up the simulation to perform debugging on c a subset of the simulated events. c DEBUG first last step c - first (int) = event number of first event to debug c - last (int) = event number of last event to debug c - step (int) = only debug one event every step events DEBUG 1 10 10000 c The following card can be used to turn off generation of secondary c particles in the simulation, ordinarily it should be 0 (or omitted). NOSECONDARIES 0 c The following card tells the simulation to store particle trajectories c in the output file. This output can be verbose, use with caution. TRAJECTORIES 0 END